The recent microelectronic technology continues to advance the miniaturization and integration of various substrates. In the case of semiconductor packaging, for example, three-dimensional packaging is employed to achieve a higher density and capacity. In the 3D semiconductor packaging technology, individual semiconductor chips are made thin and stacked in multilayer structure while they are connected by TSV (through silicon vias). To accomplish the 3D package, the step of thinning a substrate having a semiconductor circuit formed therein by back grinding and the step of forming electrodes inclusive of TSV on the back surface are necessary. As the thinning step, it is proposed to bond a substrate having a semiconductor circuit formed therein to a handle substrate of silicon, glass or the like via adhesive, yielding a substrate assembly which withstands subsequent processing steps such as back grinding and back electrode formation. After the processing steps, the handle substrate must be separated in a simple manner. After the separation of the handle substrate, the adhesive remaining on the semiconductor circuit-bearing surface of the substrate must be removed. Finally, the semiconductor circuit-bearing surface of the substrate must be cleaned. Besides, since a high temperature of above 150° C. can be encountered in the processing steps, the adhesive is required to be fully heat resistant. Thus silicone base adhesives are often used because of heat resistance.
When the substrate surface is cleaned, however, use of only an organic solvent for dissolving the adhesive is difficult to fully remove the residual adhesive. Since the substrate surface then has a contact angle with water of at least 100°, it is anticipated that failures such as defective bond of encapsulant will occur in the subsequent steps. There is a desire to have a cleaning agent capable of fully removing the residual adhesive in a short time without causing corrosion to the substrate surface. At present, there has been proposed no cleaning agent capable of fully cleaning the silicone-contaminated substrate surface in a short time.
Patent Document 1 discloses a cleaner composition for cleaning semiconductor substrates. Patent Document 2 discloses a cleaner composition comprising an organic solvent and a quaternary ammonium salt, which makes complicated the method for preparing a thin semiconductor substrate and fails to solve the problem that adhesive residues are kept on the substrate, depending on a particular type of adhesive.